Could you fail in ME1? The only failure was the forced failure choice with Kaiden/Ashley. It was plot on rails, with a few, mostly meaningless, choices along the way.
For the multiple *earned* failure options alone, I give ME2 credit.
If C&C is done poorly, it's better to keep everything on rails (which ME2 basically was). Simply completing a checklist of missions that are impossible to fail if you have an IQ over 70 is not a point in favour of ME2 (Now that I think about it, it would be a fun experiment to see how SDG would do in this game, if he manages to play it properly without a guide, I'll concede the point).
The impacts of "choices" were also portrayed terribly, making absolutely no sense at all. Since all of them are in the final hour of the game, one after the other, it's jarring. Can't even trick the player thinking it's doing something good.
That and the story it tried to present just felt more complex than whatever was going on in ME1. The idea that the reapers were some kind of galactic preservers who foresaw the Dark Energy death of the galaxy and just came around harvesting all sentient life, grinding it down and sticking it into reaper bodies was decent, if poorly executed. (The human reaper you fight at the end was dumb. Big, dumb boss fight is not how you end a sci fi game - though I guess ME1 set that precedent.)
The dark energy theory was not "poorly executed" because they didn't even try to do it, there was no attempt at execution. It was essentially completely scrapped, with only one mission in ME2 referencing it. Drew Karpyshyn was not the lead wirter of ME2, that's when Mac Walters came in, which is not ME1s fault. Because of this, ME2 is an amalgamation of 20+ unrelated side quests.
The Collectors were a good extrapolation from the mind control stuff in the previous game, and made for a much more interesting enemy than the Geth.
The collectors are not at all connected to indoctrination presented in ME1.
In ME1, indoctrination slowly changes your thought process, but if it becomes too much you lose any semblance of being a conscious being which is why you become a mindless husk who eventually dies without reapers. We saw 3 different levels of this with the Salarian prisoners on Virmire on top of Vigil telling the player what happened to the extremely indoctrinated Protheans once the Reapers left (succumbed to the elements because they couldn't think or act on their own).
Collectors on the other hand are examples of the Reapers changing the biology of species, something that really only started in ME2 (+ the retcon into saying Reapers are some dumb bio-synthetic hybrid with the entire memories of a species in them) and continued in ME3. Our only examples of this in ME1 is the Geth using spikes to turn humans into husks (these husks are different than ones we see in later games) which we can assume was reaper tech, and the theory by Vigil that Keepers were a race of beings the Reapers changed into being servants.
The connection you made between these two is really a stretch. If they were trying to make it a connection, there needed to be a lot more exposition because the only time they ever tried explaining indoctrination in the trilogy was ME1 yet it became just a convenient plot excuse explaining any type of behaviour.
Also, the entire plot of some Section 31-like secret agency bringing Shep back to life and bankrolling your Ocean's 11 adventure, including a
cigarette smoking man, was very entertaining. ME1 took itself very seriously in spite of there being very little substance, but ME2 knew to dial up the B-movie elements and give you plenty of Miranda fanservice shots along the way.
Retcons are stupid, especially when you have shit writers at Bioware who can't provide a semi-believable explanation, on games that were planned to be a connected trilogy.
ME2 dialed up B-movie elements while trying to present itself as a Hollywood blockbuster with deep character stories, which is why the atmosphere falls flat. Even ME1 had better impacting scenes, like the first time coming to the Citadel, and Sovereign attacking with the backdrop of the wards. You don't have to look deep to find an actual great B-movie tier game around the same time period. The Witcher, lots of those elements, with very specific focus on things that make it feel like a labour of love, exactly what makes those same movies feel charming. ME2 is like a pretentious failed college student making action movie slop, spending 95% of his budget on cinematics, then trying to present it as a timeless classic.
Companions were also more detailed and varied. Rex was loved in ME1 mostly because he wasn't as banal as all the other companions. Your choices were: faggot fuckboy, space racist whose dialog constantly revolves around her being a soldier, space cop lizard, big toad klingon, and latex fetish jailbait. It's no wonder ME2 opted to refresh the crew and either dump existing crew off or give them an edgy upgrade.
Characters, the most overrated aspect of ME2. 12 companions, each with their own "loyalty mission" completely separated from eachother. The absolute easiest writing you could possibly do. Take a character and do whatever you want with them with absolutely no regard for if they make sense or not. For a game that's 80% about its characters, they should've tried a bit harder. Only 4 of the companions make sense joining you (2 friends from the first game so can let that slide, and 2 that make sense with the story/plot). You can add Zaeed but considering you can't talk to him he doesn't really count as a companion in a game ALL about companions. Even with all of that, a lot of the companion missions fall flat. They made 2 half ass attempts to connect anything, Jack vs. Miranda & Tali vs. Legion, which were 2 minute scenes immediately solved through a paragon/renegade check. I can't give points to characters in a game that writes 12 disconnected short daddy issue missions. Full sidegrade at best.
ME1s characters are lacking for sure, but it's not a character piece so I can let it slide. Although if all the characters were like Wrex that would've been a lot better. Also, Ashley is not racist, and although I didn't like her as a character, she was still written well, she's the second best companion after Wrex in terms of content and nuance.
A lot of the things you pointed out about ME1 are a fault of the direction ME2 took. You have to remember ME1 is not like DA:O, it was designed and written to be the first game in a trilogy, closely connected. ME2 going off rails into something completely different hampers a lot of the aspects of ME1.